[CentOS] du vs df size difference

[Stephen John Smoogen]

On Wed, Sep 30, 2009 at 2:59 PM, Ryan Pugatch <rpug at tripadvisor.com> wrote:
> Hi all,
>
> Curious issue.. looking in to how much disk space is being used on a
> machine (CentOS 5.3).  When I compare the output of du vs df, I am
> seeing a 12GB difference with du saying 8G used and df saying 20G used.
>
> # du -hcx /
> 8.0G    total
>
> # df -h /
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/xvda3             22G   20G  637M  97% /
>
> I recognize that in most cases du and df are not going to report the
> same but I am concerned about having a 12GB disparity.  Does anyone have
> any thoughts about this or reason as to why there is a big difference?
> I have read a few articles online about it and none have really shown
> such a large difference.

One of the things I run into are either hidden files or leaked files
where a process is still talking to a file but the directory no longer
sees it so du doesn't catch it.

ls -l /proc/[0-9]*/fd/| grep delete

will show those up. Then its a matter if you want to keep that file
around or not.

also du / did not look for files in / that were starting with a .

ls -la / and see if there are hidden directories or files taking up space.

Finally sparse files can give odd readings at time.. but that is the
least likely reason.

> Thanks
>
>
>
> Ryan Pugatch
> Systems Administrator, TripAdvisor
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-- 
Stephen J Smoogen.

Ah, but a man's reach should exceed his grasp. Or what's a heaven for?
-- Robert Browning